ToDouble Method (String, IFormatProvider)

Convert.ToDouble Method (String, IFormatProvider)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Converts the specified String representation of a number to an equivalent double-precision floating point number using the specified culture-specific formatting information.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Shared Function ToDouble ( _
	value As String, _
	provider As IFormatProvider _
) As Double

Parameters

value
Type: System.String
A String containing a number to convert.
provider
Type: System.IFormatProvider
An IFormatProvider interface implementation that supplies culture-specific formatting information.

Return Value

Type: System.Double
A double-precision floating point number equivalent to the value of value.
-or-
Zero if value is Nothing.

ExceptionCondition
FormatException

value is not a number in a valid format.

OverflowException

value represents a number less than MinValue or greater than MaxValue.

The return value is the result of invoking the Double.Parse method on value.

provider is an IFormatProvider instance that obtains a NumberFormatInfo object. The NumberFormatInfo object provides culture-specific information about the format of value. If provider is Nothing, the NumberFormatInfo for the current culture is used.

If you prefer not to handle an exception if the conversion fails, you can call the Double.TryParse method instead. It returns a Boolean value that indicates whether the conversion succeeded or failed.

The following code example converts String representations of Double values with the ToDouble method, using an IFormatProvider object.


' Example of the Convert.ToDouble( String ) and 
' Convert.ToDouble( String, IFormatProvider ) methods.
Imports System.Globalization

Module Example

   Dim formatter As String = "{0,-22}{1,-20}{2}"

   ' Get the exception type name; remove the namespace prefix.
   Function GetExceptionType(ByVal ex As Exception) As String

      Dim exceptionType As String = ex.GetType().ToString()
      GetExceptionType = exceptionType.Substring( _
          exceptionType.LastIndexOf("."c) + 1)
   End Function

   Sub ConvertToDouble(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal numericStr As String, _
       ByVal provider As IFormatProvider)

      Dim defaultValue As Object
      Dim providerValue As Object

      ' Convert numericStr to Double without a format provider.
      Try
         defaultValue = Convert.ToDouble(numericStr)
      Catch ex As Exception
         defaultValue = GetExceptionType(ex)
      End Try

      ' Convert numericStr to Double with a format provider.
      Try
         providerValue = Convert.ToDouble(numericStr, provider)
      Catch ex As Exception
         providerValue = GetExceptionType(ex)
      End Try

      outputBlock.Text &= String.Format(formatter, numericStr, _
          defaultValue, providerValue) & vbCrLf
   End Sub

   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' Create a NumberFormatInfo object and set several of its
      ' properties that apply to numbers.
      Dim provider As NumberFormatInfo = New NumberFormatInfo()

      provider.NumberDecimalSeparator = ","
      provider.NumberGroupSeparator = "."
      provider.NumberGroupSizes = New Integer() {3}

      outputBlock.Text &= String.Format("This example of" & vbCrLf & _
          "  Convert.ToDouble( String ) and " & vbCrLf & _
          "  Convert.ToDouble( String, IFormatProvider ) " & _
          vbCrLf & "generates the " & _
          "following output when run in the [{0}] culture.", _
          CultureInfo.CurrentCulture.Name) & vbCrLf
      outputBlock.Text &= String.Format(vbCrLf & _
          "Several strings are converted to Double values, " & _
          "using " & vbCrLf & "default formatting " & _
          "and a NumberFormatInfo object." & vbCrLf) & vbCrLf
      outputBlock.Text &= String.Format(formatter, "String to convert", _
          "Default/exception", "Provider/exception") & vbCrLf
      outputBlock.Text &= String.Format(formatter, "-----------------", _
          "-----------------", "------------------") & vbCrLf

      ' Convert strings, with and without an IFormatProvider.
      ConvertToDouble(outputBlock, "123456789", provider)
      ConvertToDouble(outputBlock, "12345.6789", provider)
      ConvertToDouble(outputBlock, "12345,6789", provider)
      ConvertToDouble(outputBlock, "123,456.789", provider)
      ConvertToDouble(outputBlock, "123.456,789", provider)
      ConvertToDouble(outputBlock, "123,456,789.0123", provider)
      ConvertToDouble(outputBlock, "123.456.789,0123", provider)
   End Sub
End Module

' This example of
'   Convert.ToDouble( String ) and
'   Convert.ToDouble( String, IFormatProvider )
' generates the following output when run in the [en-US] culture.
' 
' Several strings are converted to Double values, using
' default formatting and a NumberFormatInfo object.
' 
' String to convert     Default/exception   Provider/exception
' -----------------     -----------------   ------------------
' 123456789             123456789           123456789
' 12345.6789            12345.6789          123456789
' 12345,6789            123456789           12345.6789
' 123,456.789           123456.789          FormatException
' 123.456,789           FormatException     123456.789
' 123,456,789.0123      123456789.0123      FormatException
' 123.456.789,0123      FormatException     123456789.0123


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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